<template>
<div>
	<router-link tag="div" to="/" class="header-abs" v-show="showAbs">
		<span class="iconfont header-abs-back">&#xe624;</span>
	</router-link>
	<div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
		<router-link to="/">
			<span class="iconfont header-fixed-back">&#xe624;</span>
		</router-link>
		景点详情
	</div>
</div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = { opacity }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  activated () {
    // 这样会造成其他页面也会检测到这个滚动事件
    window.addEventListener('scroll', this.handleScroll)
  },
  // 与 activated 有个相对的方法 deactivated
  deactivated () {
    // 解绑全局监听滚动事件
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
.header-abs
	position: absolute
	left: .2rem
	top: .2rem
	width: .8rem
	height: .8rem
	line-height: .8rem
	text-align: center
	border-radius: 50%
	background: #000
	.header-abs-back
		font-size: .4rem
		color: #fff
.header-fixed
	z-index: 2
	position: fixed
	top: 0
	left: 0
	right: 0
	height: $headerHeight
	line-height: $headerHeight
	text-align: center
	color: #fff
	background: $bgColor
	font-size: .32rem
	.header-fixed-back
		position: absolute
		top: 0
		left: 0
		width: .64rem
		text-align: center
		font-size: .4rem
		color: #fff
</style>
